Radiation therapy physics involves the application of radiation physics in cancer treatment. In this talk, I will first describe the major equipment involved in radiation treatment including medical linear accelerator (linac) and treatment planning system (TPS). Then I will talk about 3 commonly used modern treatment delivery techniques: 3D conformal, Intensity Modulated Radiation Therapy (IMRT, started around the end of 90’s) and Volume Modulated Arc Therapy (VMAT, started around 2007). Next I will talk about proton therapy and give examples of how techniques developed in basic physics research (such as Monte Carlo technique) can play a critical role in the development of proton therapy technique. In the end, I will talk about the advantage of physics major students becoming specialized in the field & their career path and briefly discuss the relationship between High Energy Physics (basic science) and Radiation Therapy Physics (applied science) based on my experience.